The invention relates to the fastening of faceplates to heat-dissipating electrical power switching devices, and more particularly, to thermally conductive faceplate fasteners securing faceplates to electrical light dimmers.
A typical prior art electrical light dimmer 10, shown in FIGS. 1 and 2, includes a body portion 14, that is ordinarily mounted in a wallbox 16, that is recess-mounted in a wall or the like. To give the dimmer a neat, clean appearance, a faceplate 18, defining a switch opening 20 therein, is usually mounted to the front of the dimmer 10 by means of fasteners 22, which are most often threaded screws.
The dimmer 10 includes a heat generating device 30, such as a triac, a field-effect transistor, or the like. In order to dissipate or carry away the heat generated by the heat generating device 30, the device is often mounted in thermal communication with a yoke 32 having a relatively high thermal conductivity, and is typically made of a metal such as aluminum. In addition to acting as a heat sink for the heat generating device 30, the yoke 32 also typically functions as a structural element to which is attached the dimmer body portion 14 and the faceplate 18.
For attaching the faceplate 18 to the yoke 32 with screws 22, the yoke 32 is usually provided with threaded holes 34 for receiving the screws 22.
Because the screws 22 are typically made of metal, a thermally conducting material, heat from the heat generating device 30 can be, and often is, transferred from the heat generating device 30, through the heat sink (or yoke) 32, to the screws 22.
In normal operation, this results in the screws 22 having a temperature greater than the ambient temperature of the environment in which the dimmer 10 is located. This poses no danger to any person or object that might come into contact with the screws 22. However, some people may find undesirable the sensation of faceplate screws 22 that feel warm to the touch. Accordingly, there is a need to provide a means for fastening a faceplate to a dimmer with screws while maintaining the temperature of the screws closer in temperature to the ambient temperature.
In accordance with the present invention, a dimmer capable of having a faceplate attached thereto by means of fasteners that are thermally insulated from any heat generating devices internal to the dimmer is presented. By thermally insulating the fasteners from any heat generating devices and their associated heat sinks, the faceplate fasteners remain at a temperature closer to that of ambient.
In addition, by thermally insulating the faceplate fasteners from any heat generating devices and heat sinks, the manufacturing of the dimmer can be simplified with a resulting lower manufacturing cost because, for example, there is no longer any need to thread the yoke.
In one embodiment, the dimmer includes a heat dissipating yoke having a first aperture therethrough for allowing the fastener to extend through or past the yoke without contacting the yoke in thermal relationship. The dimmer includes a boss defining a second aperture in axial alignment with the first aperture for receiving the fastener therein. The boss is made of a thermally insulating material, preferably having a thermal conductivity no greater than a predetermined value, such as a thermoplastic, and has a portion that extends through the first aperture to a point flush with a faceplate confronting surface of the yoke.
These and other features and advantages of the present invention will be more readily apparent from the detailed description set forth below taken in conjunction with the accompanying drawings.